This invention relates to hand tools for measuring gaps between spark plug electrodes, and in particular to such tools that also include the ability to adjust the spark plug gap if measurement indicates that the gap is of an incorrect width.
There have in the past been many different types of spark plug gauges. (See, for example, U.S. Pat. Nos. 3,045,354; 2,882,605; and 3,122,837.) An example of a spark plug measuring and adjusting tool is shown in Design Patent No. Des. 255,878, issued Jul. 15, 1980. The latter type gauges include a round opening having an interior ledge circumscribing the opening for adjusting the gap of the spark plug. However, the ledge is sized so that the side electrode is engaged at its point of connection to the body of the spark plug. When force is applied to the tool, a bend point is thus created at the junction of the side electrode with the spark plug body. The electrode shaft can thus be caused to pivot outwardly. Unfortunately, such outward pivoting of the side electrode can cause that electrode to be mis-aligned with the center electrode, reducing the efficiency of the spark plug. This outward pivoting can also cause the side electrode to interfere with insertion of the spark plug into the threaded hole in the engine block. Pressure between the threaded hole and the side electrode will also tend to narrow the gap between the side and center electrodes in this instance. Thus, although the gap between the electrodes is carefully set, the gap width can be inadvertently altered when the spark plug is inserted into the engine block. In view of these shortcomings, a need has continued to exist for an improved spark plug gap measuring and adjusting tool.